Socket plug for electrical outlets



Feb. 24, 1948. E. F. MANGOLD SOCKET PLUG FOR ELECTRICAL OUTLETS FiledJuly 10-, 1945 2 Sheets-Sheet l J m E Feb. 24, 1948.

" E. F. MANGOLD SOCKET PLUG FOR ELECTRICAL OUTLETS 2 Sheets-Eheet 2Filed July 10, 1945 Huh - amen M Eli F Man old Patented Feb. 24, 19482,436,586 SOCKET PLUG FOR ELECTRICAL OUTLETS Eli F. Marigold, Chicago,Ill., assignor of one-half to Harold P. Chapman, Columbus, OhioApplication July 10, 1945, Serial No. 604,241

1 Claim.

This invention relates to improvements in electrical outlet plugs, andhas for an object to provide a plug in which the spaced prongs thereofwill maintain firm and good electrical contact with the conductorterminals of the associated outlet fixture, whereby to minimize currentlos'ses, reduce or prevent arcing between the plug prongs and the outletterminals and maintain the plug in secure association with the outlet bypreventing accidental disengagement therebetween.

It is well known that in many instances, the usual contact plug of theprong type fits loosely in the sockets of an outlet fixture. Suchlooseness is objectionable in many respects, since if the plug isattached, for instance, to the conductor cord of such an appliance as anelectrical floor or carpet sweeper, the manipulation of the lattercauses readily the disengagement or removal of the plug from the outletfixture, requiring repeated reinsertions. This is also true ofincandescent lamps employed adjacent to machine tools where a slightcontacting of the lamp causes its cord plug to be removed from theassociated outlet. Furthermore, such looseness is apt to produceelectrical arcing between engaging contacts, and thereby forming a firehazard in addition to the premature deterioration of the fixtureconstruction.

Therefore, in accordance with the present invention and to overcome theobjects noted, among others, present in standard outlet plugconstruction, I have provided an improved contact plug in which theprongs thereof, upon insertion in the sockets of an associated outlet,are adapted to be laterally expanded, whereby to obtain improvedcurrent-transmitting engagement with the socket terminals by which theadvantages outlined are obtained.

For a further understanding of the invention, reference is to be had tothe following description and the accompanying drawings, wherein:

Fig. 1 is a perspective view of a pronged contact plug formed inaccordance with the present invention;

Fig. 2 is a vertical sectional view taken through the plug;

Fig. 3 is a similar view on the plane indicated by the line 3-3 of Fig.2;

Fig. 4 is a transverse horizontal sectional view taken on the planedisclosed by the line 4-4 of Fig. 2;

Fig. 5 is a group view showing in perspective and in a separated statethe casing halves of the plug and the thumb-actuated prong-expandingrunner;

Fig. 6 is a similar view disclosing one of the prongs of the plug andits associated expanding wedge;

Fig. 7 is a vertical sectional view taken through a modified form of acontact plug embodying the features of the present invention;

Fig. 8 is a similar view of a still further modified form.

Fig. 9 is a fragmentary edge elevational view of another modified formof plug construction;

Fig. 10 is a front elevational view of the structure disclosed in Fig.9.

Referring more particularly to the drawings, the numeral i0 designatesthe casing of my improved plug. The casing is preferably formed in twohalves, each of which being formed from a suitable insulating material.Each casing half is of integral construction and embodies a front wall II, perpendicular side walls l2 and a top wall i3. The front wall isprovided in the middle thereof with a slot M. The side walls areinwardly recessed as at l5 and terminate in spaced order to form agroove it for the reception of a cord l1 leading to the motor, or otherenergizing unit, of an electrical current-consuming appliance, notshown.

Further, each casing half includes a boss l8 having openings formedtherein, so that when said casing halves are placed together, as in Fig.3, the openings in the bosses thereof align to receive a threadedelement, such as the screw bolt l9. When assembled, the casing providesan internal chamber 20 in which is positioned the inner portions of apair of spaced contact-forming prongs 2|. Each of these prongs is formedto provide a pair of resiliently separable inner and outer bars 22 and23, respectively. The lower or inner ends of these bars are joined by anintermediate web 24.

Contiguous to the webs 24, the said bars are provided with aligningapertures for the reception of screws 25, the threaded shanks of thelatter being received within threaded openings provided in a pair ofL-shaped anchor members 26, the latter being confined in the recesses I5 when the casing halves are joined in order to hold the prongs againstlongitudinal displacement and retain the same securely in connectionwith the casing. Also, the screws 2-5 are used to unite the conductorwires of the cord I! with said prongs. The intermediate portions of theprongs 2! extend through registering slots 21 provided in the top wallsl3, and project upwardly or longitudinally forwardly from the top walls.The outer ends of the prongs may be integrally joined or the same may beseparable, as disclosed in Fig. 2, the same forming rounded surfacesadapted for insertion in the standard sockets of an outlet fixture, notshown.

In order to expand the prongs laterally upon their insertion into theoutlet sockets, I employ between the bars 22 and 23 of each prong awedge element 28. The outer or upper end of each wedge element isbeveled as at 28 and isreceived partially in an opening 30 formed in theouter bar of each prong. The wedge element is slidably positionedbetween the inner and outer bars of said prongs and at its lower end isinwardly and laterally bent as at 3|, passing through a slot 32 providedin the associated inner bar 22. These inwardly bent ends of the wedgeelements are positioned in grooves 33 provided in the sides of aslidable runner member 35, the latter being slidably received in theslots I d of the casing l0, projecting exteriorly of the outer faces ofsaid casing to provide thumb-engaging outer extremities 35'. Q

In the use and operation of the plug, the outwardly projecting ends, ofthe prongs 2| are inserted, as usual, in the receiving slots or socketsof a standard outlet fixture. Simultaneously with this insertion, theuser applies thumb pressure to the runner extremities 35, causing therunner to slide upwardly and outwardly. This movement on the part of therunner is transmitted to the wedge elements 28, moving the beveled outerends thereof forwardly so that the same spread or laterally separate thebars 22 and 23 of said prongs. By such outward flexing or spreading ofthe prong bars, the latter are brought into firm and secure frictionalengagement with the associated outlet terminals, such engagementpreventing accidental separation of the plug from the outlet, overcomesarcing between the prongs and their engaging contacts and produces goodcurrent-transmitting characteristics with low resistance values. 7

It will be noted that the prongs are expanded by the simple act ofinserting the same into the outlet sockets so that no additional time isrequired in efiecting the connection. The construction is simple yetrugged and does not add sensibly to the structural complexity ofstandard plugs in which rigid one-piece prongs are employed.

My construction is, of course, subject to certain variation ormodification without departing from its fundamental principles. Forexampl as shown in Fig. 7, the prongs 2la are longitudi nally slotted asat 36, and, in connection with each thereof, I employ a wedge element28a. Each of the latter elements comprises a metallic strip bent uponitself and formed intermediately with a flange 37, adapted to bereceived in one of the runner grooves 33. Above the flange '31, eachwedge element includes spaced arms 38 which are arranged on oppositesides of the prongs 21a, the arms 38 terminatin at their outer ends inbeveled extremities 319. By advancing the runner element forwardly, thearms 38 are moved into wedging engagement with the outlet terminals inorder to have firm and locking contact therewith.

In the modified form of the invention disclosed in Fig. 8, the wedgeelement 28?) has its outer beveled end 29b arranged in reverse order tothat disclosedin Fig. 2, so that the wedge elements 2% are movedinwardly to expand the prong arms instead of outwardly or forwardly, asin the preferred form of the invention.

In Figs. 9 and 10 of the drawings, a further modified form of theinvention has been disclosed, in which the prong 230 of the plug is oflooped formation having spaced parallel legs 45 which are joined attheir outer ends by the curved web 46. The legs 4-5 have their innersurfaces provided with adjoining semi-circular enlargements or beads ll,which may be struck inwardly from the material from which the legs 45are formed. A slidable wedge element, shown at 280, may be advancedbetween these enlargements or beads to flex the legs 45 outwardly,whereby to maintain the same in firm holding engagement with associatedcontacts.

While I have described what I consider to be several practicalembodiments of my invention, nevertheless, I reserve the right to employall other variations or modifications thereofthat may be said to fallfairly within the spirit and scope of the following claim,

I claim:

A socket plug for electrical outlets, comprising a casing composed ofseparable sections which, when assembled, provide an internal chamberhaving side walls formed with vertically extending and transverselyregistering slots, a pair of spaced metallic prongs, each of said prongshaving spaced parallel legs, said prongs being positioned within saidchamber and having forwardly projecting portions extending beyond an endwall of said casing, means for securing the inner ends of said prongs tosaid casing within the internal chamber thereof and for uniting the samewith associated electrical conductors entering an end of said casingopposed to the outwardlyprojecting ends of said prongs, a runner elementslidably mounted in said chamber, said element having exteriorlyprojecting manipulating extremities mounted for sliding movement in theslotted side walls of the casing sections, the inner legs of said prongswithin said chamber being vertically slotted, and expansion devicesjoined with said runner element and extending through the slots in theinner legs of said prongs for disposal between said legs, said devicesserving upon sliding actuation of'said runner element to expand andcontract the effective width of said prongs.

ELI F. MANGOLD.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,387.814 'Ie'n Bosch Aug. 16,1921 2,049,093 Thorin July 23, 1936 2,261,615 Cornwell Nov. 4, 19412,192,737 Folsom Mar. 5, 19410 1,536,688 Osborn May 5, 1941 1,666,729Biek et a1 Apr. 17, 1928 2,005,441 Shearer June 18, 1935 FOREIGN PATENTSNumber Country Date 351,434 Great Britain Dec. 18, 1929

